Bob Drive Propulsion

Discussion in 'Inboards' started by tom kane, Jan 15, 2010.

  1. orb353
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    orb353 Junior Member

    That is a very interesting picture. I would love to build a drive similar to that. I love the simplicity of a straight shaft drive, but I would love to be able to tilt it up slightly in the shallows. I would also love to incorporate a tunnel or pocket into the hull, to allow the prop to run a little higher, while staying submerged. That system there looks stout enough to handle the torque of turning that prop.

    tunnels, do you have any other pictures of this drive. I notice that it does not have a torque tube or torque ball, that most of the trimable(articulating) drives have. It looks well used, so I assume that for vertical trim only, the single u-joint will handle the angle?
     
  2. tunnels

    tunnels Previous Member

    YOU ARE TOTALLY MISSING THE POINT !! Think of what it could have been used for and why whoever made it like it is . fishermen made for a purpose !! it dont get any simpler than that and so practical . simple is always best !!;)
    look and build on the idea !!! you can do what ever you want
    reinvent square wheels !! dont think they will catch on but !!:(
     
  3. tom kane
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    tom kane Senior Member

    I am having computer troubles at the moment and cannot receive e-mails trying to sort it out.
    There are lots of pictures in my photos on this site and I have many more.
    The drive I built does have a torque tube (if you choose) and a self aligning thrust bearing and conventional seals.
    Do not consider a pocket in the hull it only causes many problems with interference of water flow and reduces planing surface. You can only run a prop so far out of the water about what height a surface piercing prop would run, and there is no need for a pod.There are so many ways to design a trimable drive it`s almost impossible to design a standard model. You can design a stearable drive as well. The drive works the same and has the same components as a fixed inboard drive except provision is made for the shaft to be adjusted up and down.
     
  4. orb353
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    orb353 Junior Member

    What point am I missing? That I can do whatever, build whatever I want? I already figured that out. I can build whatever I want. No disrespect intended.

    But seeing what others have built is very interesting. That is how we have gotten so far in the past 100 years, building on what others have discovered or invented before us. Facebook could never have been invented if the internet had not been invented. The internet could not have been invented without the computer.

    I just saw something unique in your photograph. Most people only buy boats, but it is so fun to work with/on them. Someone took time to build the drive in that picture, despite what is commercially available today. That is cool.

    Just because it hasn't been done, doesn't mean it cannot be done.

    I will use that picture as a stepping stone to build something useful for me.
     
  5. orb353
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    orb353 Junior Member

  6. tom kane
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    tom kane Senior Member

    Thank`s orb353. A bit expensive for me a DIY man. I have tried similar idea in smaller boat but pods and tunnels became redundant and I thought they were not necessary. That installation makes an Arson drive a much more practical build and is what a Pivotal Drive would look like if it was built to steer with.

    Image shows wedge shaped tunnel install with an outboard for trial runs before installing a Pivotal steerable Drive.
    Image shows increased plane angle of craft with tunnel fitted. Boat never achieved a flat plane angle.
     

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    Last edited: Sep 28, 2011
  7. tom kane
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    tom kane Senior Member

    Sea spray Magazine.. 1972 Set-up mounts a 4HP petrol motor on a transverse pipe in well behind cockpit.The pipe acts as a hinge so the motor and prop can be lifted...means motor drive belt and shaft are running in water...
     

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    Last edited: Sep 29, 2011
  8. powerabout
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    powerabout Senior Member

    Any part of the hull you remove from the aft means less lift aft
     
  9. orb353
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    orb353 Junior Member

    Tom, are you saying that pocket tunnels do not work? I am in the USA, and there are tons of tunnel hulls here, especially in florida. They are equipped with jack plates, that takes the outboard up and down. This allows the boat to get on a plane, then pull the outboard up, and it will run in shallow water.

    http://www.youtube.com/watch?v=wn1ijO-uo9o&feature=related

    Powerboat, alot of the tunnel/pockets hull I have seen add on to the hull slightly, on each side of the hull, to add back the lift and buoyancy. Like the one in the picture on this page

    http://www.louisianasportsman.com/l...ports&event=view&action=full_report&id=141645
     
  10. tom kane
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    tom kane Senior Member

    I did not say they do not work of course they do, but the interference to the water flow when turning and the tendency not to turn well (in an inboard) plus the loss of planing area,plus the dangerous tendency to aerate and loose thrust in a fast following sea (because the prop is set high) among some of the unwanted characteristics sent us looking for more behaved propulsion.We have tried most of the innovations related to pocket tunnels. One of my neighbors was involved with tunnels and patented (venturi principle) and sold in America different models and they were used in ocean racing with success.
    You won`t find many people who do not have some issues with what they run in their boats but would not admit to these faults.
    Image shows twin U/V joints with sliding spline and the angles you can run them in without binding, with an electric motor. This is not how you would set them up in a boat.
     

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  11. tom kane
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    tom kane Senior Member

    Model T Ford had a trimable propeller shaft and most rear drive vehicles do.
    Why should they be a problem in a boat.
     
  12. powerabout
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    powerabout Senior Member

    the plane of the 2 u joints must remain either parrallel or the same angles so the U joints cancel out each others differing accelaration and decelaration when it rotates otherwise you dont have a CV joint and hence vibration
    Study the motion of the cross its central axis moves forward and back depending on whether its drive is across or vertical, the other joint needs to be doing the exact opposite to cancel this and apply smooth output

    Thats std U joint engineering
    http://www.hurst-drivelines.com/files/Universal_Joint_Alignment_Proc_111606.pdf

    In a sterndrive the steering pivot and tilt pivot is exactly in the middle of the double joint so the top action happens
     
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  13. tom kane
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    tom kane Senior Member

    Image shows conventional set up in boats since Adam and you are saying this set up is wrong and will not work this is the same mis-information I encountered when patenting the pivotal drive. Hence the reason the patent was successful. An unexpected result from a combination of components.

    If the drive will run as in the diagrams it will also run in any other position Up, down,left,or right.
     

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  14. orb353
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    orb353 Junior Member

    Tom, I like the idea used in your photograph( the pivotal drive one). How would it be set up in a boat? That design keeps all the u joints inside the boat, which sounds good. The pulse drive, surface drive uses a similar concept, but i don't think they a thrust bearing, and they are using only one u joint, and the shaft only moves vertically, it will trim only, not steer. I also see your point about the tunnel, although with a trimable drive, you could lower the prop in a fast following sea, for the prop to get a better grip. And yes, I think everything has advantages and disadvantages, but working all of those out is alot of fun. Have you used that pivotal drive in a boat? I think your drive will work. I wonder why companies like arneson went so far as to use the torque ball and torque tube, which is much more expensive and complicated, when something like yours would do the job? I wonder if yours will handle the horsepower and torque of a large 2-5K pound boat? To propel it in planning mode?

    powerabout,
    thanks for the info on u joints. I was under my rear wheel drive truck the other day, and it indeed uses two u joints, that I understand now, cancels each other out, the differences in acceleration and deceleration.
     

  15. tom kane
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    tom kane Senior Member

    Hi orb353, I have been using Pivotal Drive since 1960`s there are some pictures in my photo album on this boatdesign.net site. Also go to www.shareaproject.com and search projects for Pivotal Brive for Boats there is information there. While you are there search projects for Safe Fuel system for boats.Any more info wanted your welcome.
     
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